Contaminated ground water can present several problems to past or present property owners or lessees. In some cases, it is the responsibility of the property owner to collect and treat the contaminated ground water to prevent it from migrating to adjacent areas. In instances where existing underground storm sewer pipes are located or pass through saturated areas of contaminated ground water, the contaminated ground water may infiltrate the storm sewer pipe through the cracks and joints. The infiltrated contaminated ground water will, by itself or mixed with storm water, flow to the outfall of the storm sewer system, bringing the contaminated ground water to the surface.
There are federal, state, and local regulations relating to required treatment of such contaminated ground water. The concentration of contaminants in infiltrated ground water flowing through and out of storm sewer pipes decreases when it mixes with the relatively higher volume of storm water flowing periodically through the storm sewer pipe. While dilution of the contaminants may be somewhat beneficial, such mixing creates relatively large volumes of contaminated water which must be treated, requiring a substantial increase in the capacity of any treatment facility. Thus, it is undesirable to allow the mixing of contaminated ground water with storm water.
Beside completely removing and replacing the preexisting storm sewer pipe, one way of segregating contaminated ground water from storm water is to line the preexisting storm water pipe with an impermeable lining. Pre-formed slip linings are well known in the art. In situ formed linings are also known, such as described in U.S. Pat. No. 4,637,754, which is incorporated herein by reference, and allow the formation of an impermeable storm water channel/flow passageway with a minimal impact on the effective flow area. Neither of these alone provide for the collection of ground water.
As mentioned above, segregation of contaminated ground water from storm water frequently must be accompanied by collection and treatment of the contaminated ground water. Various methods are known in the prior art for collection of ground water. For example, horizontal or vertical wells may be bored into the saturated area and the contaminated ground water withdrawn and treated. However, horizontal boring is expensive and inaccurate. The effectiveness of vertical boring depends upon the nature of the aquifer and the soil. For compact soil conditions, numerous and closely spaced vertical wells are required, which is expensive. Another alternative in the prior art is trenching to provide access to the contaminated ground water, as well as the use of a ground water collecting pipe buried parallel to the existing storm sewer lines.
Most of these methods are relatively expensive, and are impractical when the contaminated ground water and/or existing storm sewer pipe are located underneath existing buildings. Thus, them is a need for an economical way to collect contaminated ground water and maintain it segregated from storm water.